In a power device with a lateral metal-oxide-semiconductor (MOS) transistor structure, a lateral parasitic bipolar transistor using a drain as a collector, a body area as a base, and a source as an emitter is likely to turn on when a hole current increases due to avalanche breakdown.
When the lateral parasitic bipolar transistor turns on, the MOS transistor cannot be controlled by using a gate, so that the MOS transistor is broken down.